Any porous media, whether it is granular or continuous, is subjected to a space- and time-variant stress field. This stress field determines the behavior of the geological formation, and depending on the stress state of the geological formation, the geological formation may exhibit very different phenomena.
Operations performed on the porous media may lead to changes in the stress field. This change in the stress field may result in problems such as sand production seen in the recovery of hydrocarbons. The removal of hydrocarbons from a rock formation causes a deterioration of the stress field and results in the loosening of the formation next to the wellbore. The production of such sand or formation material along with production fluids tends to cause erosion and/or plugging of production equipment, substantially increasing the costs of well operation.
Current methods of altering the stress field of geological formations include resin consolidation. U.S. Pat. No. 3,404,735, entitled “Sand Control Method” and U.S. Pat. No. 5,178,218, entitled “Methods of Sand Consolidation with Resin”, disclose using resins to form permeable consolidated zones around wells. In general, a curable resin, often a thermosetting polymer, is injected into a wellbore and caused to harden thus consolidating the solids into a hard permeable mass. The resin forms a coating around individual particles and binds the particles together, which increases the yield strength of the geological formation. As a result, the stress field becomes more uniform as the formation is able to distribute loads into the newly consolidated portions and sand production may be reduced. One of the difficulties encountered during the implementation of resin consolidation is unintended plugging of certain low-permeability regions of the formation. A further difficulty encountered may be poor adhesion between particles which detracts from the effectiveness of resin consolidation.
A further approach to altering the stress field of the formation involves high-pressure injection of incompressible materials. Common materials utilized are water, gravel and specialized fluid/proppant mixtures. U.S. Pat. No. 6,382,319, entitled “Method and Apparatus for open hole gravel packing” discloses an open hole gravel packing system wherein a positive hydrostatic pressure differential within the wellbore is maintained against the production formation walls throughout all phases of the gravel packing procedure. U.S. Pat. No. 5,531,274, entitled “Lightweight proppants and their use in hydraulic fracturing” discloses lightweight proppants and U.S. Pat. No. 7,144,844, entitled “Method of using viscoelastic vesicular fluids to enhance productivity of formations” discloses the use of viscoelastic fluids, such as diverter fluids in matrix acidizing, fracturing fluids and fluids for sand control completion. One of the difficulties with these methods is the significant cost associated with high-pressure injection. A further significant problem is the risk associated with failure of the well equipment.
However, there still remains a need for improved apparatus and methods for consolidating, or at least partially consolidating production formations to prevent the migration of sand material along with production fluids from a production formation while at the same time maintaining permeability in the production zone.